The Fabrication And Optic-Property Studying Of Polymer Dispersed Liquid Crystals Films

The liquid crystals are used to parts of a display apparatus widely as display materials. The study on new performance of liquid crystals propels the development of economy and modernization. The liquid crystals are used to mobile, computer, notebook PC and bigger display as display materials. The liquid crystal polymer is used to fibre materials, bullet-proof clothing and display because of the high modulus and highly elastic performance. The liquid crystal inomers are interested for the particular performance by pursuers. The liquid crystal inomer and PDLC are interested by pursuers as a novel kind of liquid crystals material lately. PDLC are a novel functional liquid crystal composites material. The liquid crystal droplets are dispersed in polymer matrix in nano-or micrometer. The novel liquid crystal materials are interested for the high sensitivity, widely dynamic, high resolving power, rapidly response time and easy molding of polymer.The PDLC films are fabricated by phase separation. The prepolymer and liquid crystal are mixed in homogeneous mixture. When the prepolymer was polymerized by polycondensation, radical polymerization or light-initiated polymerization, the chains of polymer are lengthened and the solubility of liquid crystal is shrunk. The PDLC films are fabricated by phase separation of polymer and liquid crystal. The PDLC films are fabricated by solvent evaporation in mixture of polymer and liquid crystals which dissolved in same solvent. The microcapsule is an effective method to fabricate the PDLC films.The director of liquid crystal droplets is orientated to direction of electric field when the electric field was applied to PDLC films. When the refractive index of liquid crystal equals to polymer, the PDLC film is transparent state. When the electric field is removed, the PDLC films is scattering state for the director of liquid crystal is clutter and the refractive index of liquid crystal not match to polymer. We can comprehend that the liquid crystal droplets are bipolar ellipsoid for the high anchoring energy between polymer and liquid crystals and presented scattering state. The director of liquid crystal was homogeneous orientated to electric field and presented transparent state.The merit of PDLC films are none-polarizer, high brightness, wide angle and none-alignment layer as to traditional LCD. The PDLC films are potential used to bigger display for the novel merit. The electro-optic and response time properties of PDLC films are widely study by lots of team. At present, it is difficulty to fabricate high contrast, low threshold and saturation voltage, rapid responsiveness and high stability PDLC films. To influence the performance of PDLC films’ factor are (1) the performance and structure of materials;(2) the morphology of PDLC films;(3) the dielectric of polymer matrix;(4) the condition of the fabrication of PDLC films.In this paper, the polymer matrix is composed by tri-functional prepolymer and epoxy resins. The smaller liquid crystal droplets are obtained by rapid polymerization which initiated by ultraviolet lights in tri-functional prepolymer. We fabricate four series of PDLC films which composed by chiral liquid crystal, nano-graphites and polymerizable polar molecules respectively. The doped materials enhance the electro-optical performance of PDLC films. The main works in this paper are as following:(1) Effect of thermal and electric field on optical performance of chiral PDLC film are studied. The changes of optic rotation which affect by thermal and electric field are equal to theory of de Vries. The morphology of chiral PDLC film is observed by POM, SEM and infrared images. The diameter of liquid crystal droplets is estimated by infrared images and POM photographs and obtains the same results in5μm.(2) The nano-graphites doped PDLC films are fabricated. The doped nano-graphites enhance the dielectric of polymer and reduce the threshold and saturation voltage.(3) We fabricate the acrylic acid doped PDLC films. The effect of doped acrylic acid on kinetic of polymerization is observed by change of real time transmittance. The doped acrylic acid improves the electro-optic of PDLC films according the reducing of threshold and saturation voltage.(4) The kinetic of polymerization of polymerizable polar molecules doped PDLC films is studied by changing of real time transmittance. The effect of doped polymerizable polar molecules on electro-optic of PDLC films is studied.In summery, the research of present study not only in the further investigation on the effect of polymerization condition on polymerization induced phase separation, but also in the improvement of electro-optical performance of PDLC films. The doped nano-graphites, pelymerizable polar molecules are effectively improving the performance of PDLC films.